Surveying Scotland's seas

Pobie Bank Reef in the spotlight

In late August, JNCC staff joined colleagues from
Marine Scotland
Science aboard the MRV Scotia for a two week survey of
the Pobie Bank Reef candidate Special Area of
Conservation (cSAC). Located approximately 20km east of Shetland,
Pobie Bank Reef is made up of stony and bedrock reef, surrounded by
a mixture of sediments. The aim of the survey was to gather
evidence to improve understanding of seabed character and the
distribution of benthic communities within the site. As fishing for
seabed species currently occurs in certain areas of the site,
further understanding of the sensitivity will facilitate future
fisheries management.

Reaching 70km in length and 21km wide, the
cSAC covers a large area which was divided up into four priority
blocks to focus the data collection. The survey team began by
collecting acoustic data, using sidescan sonar and a multibeam
echosounder to build up a picture of the type of seabed habitats
present. The data collected enabled the identification of rock
formations, different sediment types and even underwater pipelines
on the seabed.

Following processing by colleagues from the
British Geological Survey, the acoustic
data was used to help identify areas of potential rocky or stony
reef, where the ground-truthing work could be
focused. Ground-truthing involves towing a camera just above
the seafloor, to film and photograph the seabed and build up a
picture of the species and habitats present. Watching the live feed
from the video the team saw a number of species including sponges,
cup corals, anemones, and several species of fish - a ling followed
the camera plum line for several metres! They could also see
how the seabed habitats changed from boulders and bedrock, to areas
of sandy sediment. Depth also influenced the communities
found on the seabed; pink coralline algae were found in shallower
areas where light levels were higher, whereas sponge communities
were found at deeper sites.

Where sediment was found, the team were able
to collect samples from the seafloor using a hamon or day
grab. The samples will be analysed in a laboratory to
determine exactly what type of sediment was in the sample and also
to identify any burrowing animals that may be present.

After two weeks at sea, the Scotia was
welcomed back into Aberdeen harbour in the evening of 6 September.
Once the data collected has been analysed, it will be passed on to
the SAC Management Advice team who are leading JNCC’s advice to
Government on management measures for offshore SACs.